Worker bees possibly harmed by pesticides: experts

Taiwanese academics say the symptoms of colony collapse disorder (CCD) in Taiwan may not fit the classic definition for CCD, which is likely to be due to pesticide poisoning.

CCD is a phenomenon in which worker bees from a beehive abruptly disappear. While not a modern phenomenon, the syndrome has caught the attention of scientists after a drastic rise in the number of disappearances of Western honeybee colonies in North America and Europe in 2006.

CCD has been alleged to be a reason for reduced agricultural production in certain areas.

National Ilan University Biotechnology and Animal Science Departmebt director Chen Yue-wen (陳裕文) said that an investigation conducted by the university showed a beekeeper with more than 70 years of experience to have recently suffered a great loss in his bee stock, with 95 out of 100 hives dying within one month.

Tests showed that most of his bees had died from pesticide poisoning, Chen said, adding that the pesticides originated primarily from nearby fruit orchards.

Chen said he spent the latter part of last year running tests on 41 samples of pollen from all around the nation, and found only 5 samples to be free from pesticide residue, adding that tau-fluvalinate and chlorpyrifos residues showed up in 66 and 61 percent of the samples respectively.

Chen said he suspected that CCD in Taiwan may be caused by excessive use of pesticide by farmers.

National Taiwan University entomology professor Yang En-cheng (楊恩誠) said his recent studies showed that the notion that only a high concentration of pesticides would affect honeybees could be incorrect.

Honeybees could be affected even by low concentrations of pesticide, Yang said.

Bees die from acute toxic substances, but should they survive and return to the hive, the larvae would be nourished with nectar and pollen contaminated with low concentrations of pesticide, Yang said, adding that the pesticide interferes with the larva’s neural systems, memory and capacity for learning.

Once the larva matures into a worker bee, it would not be able to sustain the hive with pollen, honey and water gathering, which would rapidly affect the entire hive, affecting its ability to survive and killing off the population, Yang said.

However, a beekeeper in Taoyuan County’s Longtan Townshsip (龍潭), Chiang Hu-tsai (江虎才), said that worker bees had a foraging range of 5km, and the distance was far enough for any bee to have come into contact with pesticide — no matter the concentration — to succumb to the toxicity before returning to the hive.

There are many reasons causing mass deaths of bees, but none have been confirmed to have a direct linkage with pesticide, Chiang said, adding that National Ilan University’s investigation should be studied more closely.

“We need more data on before drawing a conclusion,” Chiang said, adding that bees can get sick as well, such as coming down with the American or European foulbrood sickness or an infestation of varroa mites.

According to Taiwan Beekeepers Association chairman Wu Chao-sheng (吳朝生), domestic honey production has dropped by 50 percent this year, with between 8,000 tonnes and 9,000 tonnes that will be sold on the market.

He added that he “felt the lack of honey and mass deaths of bees is due to worker bees not being able to find pollen and being overworked and has nothing to do with pesticides.”